cli: add -v and -h shorthands

cli: add -v and -h shorthands

Change the behavior of "git -v" to be synonymous with "--version" /
"version", and "git -h" to be synonymous with "--help", but not "help".

These shorthands both display the "unknown option" message. Following
this change, "-v" displays the version, and "-h" displays the help text
of the "git" command.

It should be noted that the "-v" shorthand could be misinterpreted by
the user to mean "verbose" instead of "version", since some sub-commands
make use of it in this context. The top-level "git" command does not
have a "verbose" flag, so it's safe to introduce this shorthand
unambiguously.

Signed-off-by: Garrit Franke <garrit@slashdev.space>
Signed-off-by: Junio C Hamano <gitster@pobox.com>